Thyroid Dysfunction Detected in Intensively Cared Neonates for More than 1 Month

Kim, Jeong Ok; Lee, Ji Hyuk; Lee, Jang Hun; Han, Heon Seok

Abstract

PURPOSE: To evaluate the incidence, time of detection, classification, and risk factors of thyroid dysfunction in neonates at a neonatal intensive care unit.
METHODS
This is a retrospective study reviewing medical records of 67 infants (including 40 very low birth weight infants, VLBW), who were admitted for more than 1 month at Chungbuk National University Hospital from July 2006 to June 2009. Initial screening and repeat thyroid function tests were performed before and after two weeks of age.
RESULTS
1) In the thyroid dysfunctional group (42/67, 62.7% including 30 VLBW), only 9 infants (including 8 VLBW) were abnormal at screening. Among 57 infants with normal screening, 33 infants (57.9%, including 22 VLBW) changed to abnormal at follow-up. The detection times at the repeat test were 2-4 weeks of age (WA) (n = 15), 4-6 WA (n = 15), and 6-8 WA (n = 3). 2) The types of dysfunction were primary hypothyroidism (PH) with marked TSH rise (n = 7), mild PH (n = 3), hyperthyrotropinemia (n = 11), hypothyroxinemia (n = 7), and non-thyroidal illness (n = 14). 3) Compared to the normal group (n = 25), the dysfunctional group (n = 42) had lower birth weight, shorter gestational age, and more morbidity of respiratory distress syndrome (P < 0.05). 4) Thyroxine was prescribed in 15cases (35.7%) in the dysfunctional group except non-thyroidal illness.
CONCLUSION
Thyroid dysfunction was common in the intensively cared neonates, especially in VLBW, and many cases were detected at the repeat test. The thyroid function test should therefore be repeated at least from 2 WA to 8 WA, and a proper management plan established by investigate the characteristics and long-term prognosis of these neonates.